Key Cutting For "Patented" key

Hi

I have just started to lease a property and today went to get a couple of extra keys cut. However, the locksmith (just at the market) said he couldn't do it as it said "patented" on it. I've googled it and it says you need a letter of authorisation to get a copy of these sort of keys cut. I've never come across this before and have no idea how I would go about get "authorisation." The key does have a number on it which I think is the "pattern" of the key. Does anyone know anywhere where I could get a key cut in sheffield that has the patented mark on it?

Thanks

No you can't , you need to see your lease agent they will normally have a card with the details on it , this will all depend on key make eg Union , kaba , ect

Ok. At the moment I don't have direct access to them which is a pain. I'm waiting for them to contact me so I have contact details etc. It says "mla" on they key which I presume is the make

The idea behind these keys is so that (for instance) you cannot get a spare key cut which the landlord does not know about, and let yourself in after you finish renting the house. This saves the landlord from having to change the locks after every tenant leaves.

MLA may mean Master Locksmith Association